Several expansions of populations of

archaic humans ''Homo'' () is a genus of great ape (family Hominidae) that emerged from the genus ''Australopithecus'' and encompasses only a single extant species, ''Homo sapiens'' (modern humans), along with a number of extinct species (collectively calle ...

(genus ''

Homo ''Homo'' () is a genus of great ape (family Hominidae) that emerged from the genus ''Australopithecus'' and encompasses only a single extant species, ''Homo sapiens'' (modern humans), along with a number of extinct species (collectively called ...

'') out of Africa and throughout Eurasia took place in the course of the Lower Paleolithic, and into the beginning

Middle Paleolithic The Middle Paleolithic (or Middle Palaeolithic) is the second subdivision of the Paleolithic or Old Stone Age as it is understood in Europe, Africa and Asia. The term Middle Stone Age is used as an equivalent or a synonym for the Middle P ...

, between about 2.1 million and 0.2 million years ago (Ma). These expansions are collectively known as Out of Africa I, in contrast to the expansion of

anatomically modern humans Early modern human (EMH), or anatomically modern human (AMH), are terms used to distinguish ''Homo sapiens'' ( sometimes ''Homo sapiens sapiens'') that are anatomically consistent with the range of phenotypes seen in contemporary humans, from ...

(''

Homo sapiens Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

'') into Eurasia, which may have begun shortly after 0.2 million years ago (known in this context as " Out of Africa II"). The earliest presence of ''Homo'' (or indeed any

hominin The Hominini (hominins) form a taxonomic tribe of the subfamily Homininae (hominines). They comprise two extant genera: ''Homo'' (humans) and '' Pan'' (chimpanzees and bonobos), and in standard usage exclude the genus '' Gorilla'' ( gorillas) ...

) outside of Africa dates to close to 2 million years ago. A 2018 study identified hominin presence at Shangchen, central China, as early as 2.12 Ma based on magnetostratigraphic dating of the lowest layer containing stone artefacts. "Eight major magnetozones are recorded in the Shangchen section, four of which have normal polarity (N1 to N4) and four of which have reversed polarity (R1 to R4). By comparison with the geomagnetic polarity timescale ..magnetozone N4 corresponds to the Réunion excursion (2.13–2.15 Ma) in L28." The oldest known human skeletal remains outside of Africa are from

Dmanisi Dmanisi ( ka, დმანისი, tr, , ) is a town and archaeological site in the Kvemo Kartli region of Georgia (country), Georgia approximately 93 km southwest of the nation’s capital Tbilisi in the river valley of Mashavera. Abandoned i ...

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

( Dmanisi skull 4), and are dated to 1.8 Ma. These remains are classified as '' Homo erectus georgicus''. Later waves of expansion are proposed around 1.4 Ma (early Acheulean industries), associated with ''

Homo antecessor ''Homo antecessor'' (Latin "pioneer man") is an extinct species of archaic human recorded in the Spanish Archaeological Site of Atapuerca, Sierra de Atapuerca, a productive archaeological site, from 1.2 to 0.8 million years ago during the Early ...

'' and 0.8 Ma ( cleaver-producing Acheulean groups), associated with ''

Homo heidelbergensis ''Homo heidelbergensis'' is a species of archaic human from the Middle Pleistocene of Europe and Africa, as well as potentially Asia depending on the taxonomic convention used. The species-level classification of ''Homo'' during the Middle Pleis ...

''. Until the early 1980s, early humans were thought to have been restricted to the African continent in the

Early Pleistocene The Early Pleistocene is an unofficial epoch (geology), sub-epoch in the international geologic timescale in chronostratigraphy, representing the earliest division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently esti ...

, or until about 0.8 Ma; Hominin migrations outside East Africa were apparently rare in the Early Pleistocene, leaving a fragmentary record of events.

Early dispersals

Pre-''Homo'' hominin expansion out of Africa is suggested by the presence of '' Graecopithecus'' and '' Ouranopithecus'', found in Greece and Anatolia and dated to c. 8 million years ago, but these are probably

Homininae Homininae (the hominines) is a subfamily of the family Hominidae (hominids). (The Homininae——encompass humans, and are also called "African hominids" or "African apes".) This subfamily includes two tribes, Hominini and Gorillini, both having ...

but not Hominini. Possibly related are the Trachilos footprints found in Crete, dated to close to 6 million years ago; the age of the footprints was later reestimated to be 6.05 million years ago, 0.35 million years older than previous estimations. Another reestimation by Willem Jan Zachariasse and Lucas Lourens interpret the purported footprints to have originated 3 million years ago and doubt if they were footprints or the hominins had made the footprints because of the shallow marine setting and the separation of Crete from mainland Greece and Turkey in the Late Pliocene by the South Aegean Basin. '' Australopithecina'' emerged about 5.6 million years ago, in East Africa ( Afar Depression). Gracile australopithecines (''

Australopithecus afarensis ''Australopithecus afarensis'' is an extinct species of australopithecine which lived from about 3.9–2.9 million years ago (mya) in the Pliocene of East Africa. The first fossils were discovered in the 1930s, but major fossil finds would not ta ...

'') emerged in the same region, around 4 million years ago. The earliest known retouched tools were found in

Lomekwi Lomekwi is an archaeological site located on the west bank of Turkana Lake in Kenya. It is an important milestone in the history of human archaeology. An archaeological team from Stony Brook University in the United States discovered traces o ...

, Kenya, and date back to 3.3 Ma, in the late

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Australopithecus garhi'' or ''

Paranthropus aethiopicus ''Paranthropus aethiopicus'' is an Extinction, extinct species of robust australopithecine from the Late Pliocene to Early Pleistocene of East Africa about 2.7–2.3 million years ago. However, it is much debated whether or not ''Paranthropus'' ...

'', the two known hominins contemporary with the tools. Genus ''

'' is assumed to have emerged by around 2.8 million years ago, with ''

Homo habilis ''Homo habilis'' ( 'handy man') is an extinct species of archaic human from the Early Pleistocene of East and South Africa about 2.4 million years ago to 1.65 million years ago ( mya). Upon species description in 1964, ''H. habilis'' was highly ...

'' being found at Lake Turkana,

Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...

. The delineation of the "human" genus, ''

'', from Australopithecus is somewhat contentious, for which reason the superordinate term "hominin" is often used to include both. "Hominin" technically includes chimpanzees as well as pre-human species as old as 10 million years old (the separation of

into Hominini and

Gorillini Gorillini is a taxonomic tribe containing three genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomencla ...

). The earliest known hominin presence outside of Africa dates to close to 2 million years ago. A 2018 study claims evidence for human presence at Shangchen, central China, as early as 2.12 Ma based on magnetostratigraphic dating of the lowest layer containing stone artefacts. It has been suggested that ''

Homo floresiensis ''Homo floresiensis'' , also known as "Flores Man" or "Hobbit" (after Hobbit, the fictional species), is an Extinction, extinct species of small archaic humans that inhabited the island of Flores, Indonesia, until the arrival of Homo sapiens, ...

'' was descended from such an early expansion. It is not clear whether these earliest hominins leaving Africa should be considered ''Homo habilis'', or a form of early ''Homo'' or late ''Australopithecus'' closely related to ''Homo habilis'', or a very early form of ''Homo erectus''. In any case, the morphology of ''H. floresiensis'' has been found to show greatest similarity with ''

Australopithecus sediba ''Australopithecus sediba'' is an extinct species of australopithecine recovered from Malapa Fossil Site, Cradle of Humankind, Malapa Cave, Cradle of Humankind, South Africa. It is known from a partial juvenile skeleton, the holotype MH1, and a ...

'', ''

'' and Dmanisi Man, raising the possibility that the ancestors of ''H. floresiensis'' left Africa before the appearance of ''H. erectus''. A

phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

published in 2017 suggests that ''H. floresiensis'' was descended from a species (presumably Australopithecine) ancestral to ''

'', making it a "sister species" either to ''H. habilis'' or to a minimally ''habilis''-''erectus''-''ergaster''-''sapiens''

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

, and its line is older than ''H. erectus'' itself. On the basis of this classification, ''H. floresiensis'' is hypothesized to represent a hitherto unknown and very early migration out of Africa, dating to before 2.1 million years ago. A similar conclusion is suggested by the date of 2.1 Ma for the oldest Shangchen artefacts.

''Homo erectus''

Homo erectus ''Homo erectus'' ( ) is an extinction, extinct species of Homo, archaic human from the Pleistocene, spanning nearly 2 million years. It is the first human species to evolve a humanlike body plan and human gait, gait, to early expansions of h ...

'' emerges just after 2 million years ago. Early ''H. erectus'' would have lived face to face with ''H. habilis'' in East Africa for nearly half a million years. The oldest ''Homo erectus'' fossils appear almost contemporaneously, shortly after two million years ago, both in Africa and in the Caucasus. The earliest well-dated Eurasian ''H. erectus'' site (if the fossils are indeed ''H. erectus'' — see Dmanisi hominins) is

in Georgia, securely dated to 1.8 Ma.1.85-1.78 Ma 95% CI. A skull found at Dmanisi is evidence for caring for the old. The skull shows that this ''Homo erectus'' was advanced in age and had lost all but one tooth years before death, and it is perhaps unlikely that this hominid would have survived alone. It is not certain, however, that this is sufficient proof for caring – a partially paralysed chimpanzee at the Gombe reserve survived for years without help. The earliest known evidence for African ''H. erectus'', dubbed '' Homo ergaster'', is a single occipital bone (KNM-ER 2598), described as "H. erectus-like", and dated to about 1.9 Ma (contemporary with ''

Homo rudolfensis ''Homo rudolfensis'' is an extinct species of archaic human from the Early Pleistocene of East Africa about 2 million years ago (mya). Because ''H. rudolfensis'' coexisted with several other hominins, it is debated what specimens can be confiden ...

''). This is followed by a fossil gap, the next available fossil being KNM-ER 3733, a skull dated to 1.6 Ma.

sites in North Africa, the geographical intermediate of East Africa and Georgia, are in poor stratigraphic context. The earliest of the dated is Ain Hanech in northern

Algeria Algeria, officially the People's Democratic Republic of Algeria, is a country in the Maghreb region of North Africa. It is bordered to Algeria–Tunisia border, the northeast by Tunisia; to Algeria–Libya border, the east by Libya; to Alger ...

(c. 1.8 – 1.2 Ma), an Oldowan grade layer. These sites attest that early ''Homo erectus'' have crossed the North African tracts, which are usually hot and dry. There is little time between ''Homo erectus apparent arrival in

South Caucasus The South Caucasus, also known as Transcaucasia or the Transcaucasus, is a geographical region on the border of Eastern Europe and West Asia, straddling the southern Caucasus Mountains. The South Caucasus roughly corresponds to modern Armenia, ...

around 1.8 Ma, and its probable arrival in East and Southeast Asia. There is evidence of ''H. erectus'' in Yuanmou, China, dating to 1.7 Ma and in Sangiran, on

Java Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...

, Indonesia, from 1.66 Ma. Ferring et al. (2011) suggest that it was still ''

'' that reached West Asia, and that early ''H. erectus'' developed there. ''H. erectus'' would then have dispersed from West Asia, to East Asia (

Peking Man Peking Man (''Homo erectus pekinensis'', originally "''Sinanthropus pekinensis''") is a subspecies of '' H. erectus'' which inhabited what is now northern China during the Middle Pleistocene. Its fossils have been found in a cave some southw ...

) Southeast Asia ( Java Man), back to Africa ('' Homo ergaster''), and to Europe ( Tautavel Man). It appears ''H. erectus'' took longer to move into Europe, the earliest site being Barranco León in southeastern

Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

dated to 1.4 Ma, associated with ''

'', and a controversial Pirro Nord in Southern Italy, allegedly from 1.7 – 1.3 Ma. The paleobiogeography of early human dispersals in western Eurasia characterizes ''H''. ex gr. ''erectus'' as a temperature sensitive stenobiont, that failed to disperse north of the Alpide Belt. The geographically restricted earliest human presence in the

Iberian Peninsula The Iberian Peninsula ( ), also known as Iberia, is a peninsula in south-western Europe. Mostly separated from the rest of the European landmass by the Pyrenees, it includes the territories of peninsular Spain and Continental Portugal, comprisin ...

should be regarded as evidence of a sustainable presence of human population in this isolated area. The Pannonian plain, situated south-west of the

Carpathian Mountains The Carpathian Mountains or Carpathians () are a range of mountains forming an arc across Central Europe and Southeast Europe. Roughly long, it is the third-longest European mountain range after the Ural Mountains, Urals at and the Scandinav ...

, was apparently characterized by a comparatively warm climate similar to that of the Mediterranean Area, while the climate of the western European paleobiogeographic area was mitigated by

Gulf Stream The Gulf Stream is a warm and swift Atlantic ocean current that originates in the Gulf of Mexico and flows through the Straits of Florida and up the eastern coastline of the United States, then veers east near 36°N latitude (North Carolin ...

influence and could support the episodic hominin dispersals toward the

. Apparently, the faunal exchanges between southeastern Europe and the Near East and southern Asia were controlled by the complex interaction of such geographic obstacles as the

Bosporus The Bosporus or Bosphorus Strait ( ; , colloquially ) is a natural strait and an internationally significant waterway located in Istanbul, Turkey. The Bosporus connects the Black Sea to the Sea of Marmara and forms one of the continental bo ...

and the

Manych The Manych () is a river in the Black Sea–Caspian Steppe of Southern Russia. It flows through the western and central part of the Kuma–Manych Depression. In ancient times, it was known as the Lik. A tributary of the Don (river), Don, it is l ...

Strait, the climate barrier from the north of the Greater Caucasus range, and the 41 kyr glacial Milankovitch cycles that repeatedly closed the Bosporus and thus triggered the two-way faunal exchange between

southeastern Europe Southeast Europe or Southeastern Europe is a geographical sub-region of Europe, consisting primarily of the region of the Balkans, as well as adjacent regions and Archipelago, archipelagos. There are overlapping and conflicting definitions of t ...

and the

Near East The Near East () is a transcontinental region around the Eastern Mediterranean encompassing the historical Fertile Crescent, the Levant, Anatolia, Egypt, Mesopotamia, and coastal areas of the Arabian Peninsula. The term was invented in the 20th ...

, and, apparently, the further westward dispersal of the archaic hominins in Eurasia. By 1 Ma, ''Homo erectus'' had spread across Eurasia (mostly restricted to latitudes south of the

50th parallel north Following are circles of latitude between the 45th parallel north and the 50th parallel north: 46th parallel north The 46th parallel north is a circle of latitude that is 46 degree (angle), degrees true north, north of the Earth, Earth's equat ...

). It is hard to say, however, whether settlement was continuous in Western Europe, or if successive waves repopulated the territory in glacial interludes. Early Acheulean tools at Ubeidiya from 1.4 Ma is some evidence for a continuous settlement in the West, as successive waves out of Africa after then would likely have brought Acheulean technology to Western Europe. The presence of Lower Paleolithic human remains in Indonesian islands is good evidence for seafaring by ''Homo erectus'' late in the

. Bednarik suggests that navigation had appeared by 1 Ma, possibly to exploit offshore fishing grounds. He has reproduced a primitive dirigible (steerable) raft to demonstrate the feasibility of faring across the

Lombok Strait The Lombok Strait () is a strait of the Bali Sea connecting to the Indian Ocean, and is located between the islands of Bali and Lombok in Indonesia. The Gili Islands are on the Lombok side. Its narrowest point is at its southern opening, with a ...

on such a device, which he believes to have been done before 850 ka. The strait has maintained a width of at least 20 km for the whole of the Pleistocene. Such an achievement by ''Homo erectus'' in the Early Pleistocene offers some strength to the suggested water routes out of Africa, as the

Gibraltar Gibraltar ( , ) is a British Overseas Territories, British Overseas Territory and British overseas cities, city located at the southern tip of the Iberian Peninsula, on the Bay of Gibraltar, near the exit of the Mediterranean Sea into the A ...

, Sicilian, and Bab-el-Mandeb exit routes are harder to consider if watercraft are deemed beyond the capacities of ''Homo erectus''.

''Homo heidelbergensis''

Archaic humans in Europe beginning about 0.8 Ma ( cleaver-producing Acheulean groups) are classified as a separate, erectus-derived species, known as ''

''. ''H. heidelbergensis'' from about 0.4 Ma develops its own characteristic industry, known as Clactonian. ''H. heidelbergensis'' is closely related to '' Homo rhodesiensis'' (also identified as ''Homo heidelbergensis sensu lato'' or African ''H. heidelbergensis''), known to be present in southern Africa by 0.3 Ma. ''

'' emerges in Africa before about 0.3 Ma from a lineage closely related to early ''H. heidelbergensis''. The first wave of " Out of Africa II and "earliest presence of ''H. sapiens'' in West Asia, may date to between .3 and 0.2 Ma, and ascertained for 0.13 Ma. Genetic research also indicates that a later migration wave of ''H. sapiens'' (from .07-.05 Ma) from Africa is responsible for all to most of the ancestry of current non-African populations.

Routes out of Africa

Most attention as to the route taken from Africa to West Asia is given to the Levantine land corridor and the Bab-el-Mandeb straits. The latter separates the Horn of Africa and Arabia, and may have allowed dry passage during some periods of the Pleistocene. Another candidate is the

Strait of Gibraltar The Strait of Gibraltar is a narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Europe from Africa. The two continents are separated by 7.7 nautical miles (14.2 kilometers, 8.9 miles) at its narrowest point. Fe ...

. A route across the

Strait of Sicily The Strait of Sicily (also known as Sicilian Strait, Sicilian Channel, Channel of Sicily, Sicilian Narrows and Pantelleria Channel; or the ; or , ' or ') is the strait between Sicily and Tunisia. The strait is about wide and divides the Ty ...

was suggested in the 1970s but is now considered unlikely.

Levantine corridor

The use by hominins of the Levantine corridor, connecting

Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...

via the

Sinai peninsula The Sinai Peninsula, or simply Sinai ( ; ; ; ), is a peninsula in Egypt, and the only part of the country located in Asia. It is between the Mediterranean Sea to the north and the Red Sea to the south, and is a land bridge between Asia and Afri ...

with the

Eastern Mediterranean The Eastern Mediterranean is a loosely delimited region comprising the easternmost portion of the Mediterranean Sea, and well as the adjoining land—often defined as the countries around the Levantine Sea. It includes the southern half of Turkey ...

, has been associated to the phenomenon of rising and declining humidity of the desert belt of northern Africa, known as the Sahara pump. The numerous hominin sites in the Levant, such as Ubeidiya and Misliya cave, are used as indicators of this migration route. As of 2012, the genetic analysis of human populations in Africa and Eurasia supports the concept that during the

Paleolithic The Paleolithic or Palaeolithic ( years ago) ( ), also called the Old Stone Age (), is a period in human prehistory that is distinguished by the original development of stone tools, and which represents almost the entire period of human prehist ...

and

Mesolithic The Mesolithic (Ancient Greek language, Greek: μέσος, ''mesos'' 'middle' + λίθος, ''lithos'' 'stone') or Middle Stone Age is the Old World archaeological period between the Upper Paleolithic and the Neolithic. The term Epipaleolithic i ...

periods, this route was more important for bi-directional human migrations between Africa and Eurasia than was the Horn of Africa.

Horn of Africa to Arabia (Bab el-Mandeb)

Bab-el-Mandeb is a 30 km strait between East Africa and the Arabian Peninsula, with a small island, Perim, 3 km off the Arabian bank. The strait has a major appeal in the study of Eurasian expansion in that it brings East Africa close to Eurasia. It does not require hopping from one water body to the next across the North African desert. The land connection with Arabia disappeared in the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58evaporite An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as oce ...

deposits after 600 years. Neither have been detected. A strong current flows from the Red Sea into the Indian Ocean and crossing would have been difficult without a land connection. Oldowan grade tools are reported from Perim Island, implying that the strait could have been crossed in the Early Pleistocene, but these finds have yet to be confirmed.

Strait of Gibraltar

The

is the Atlantic entryway to the Mediterranean, where Spanish and Moroccan banks are only 14 km apart. A decrease in sea levels in the Pleistocene due to

glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate be ...

would not have brought this down to less than 10 km. Deep currents push westwards, and surface water flows strongly back into the Mediterranean. Entrance into Eurasia across the strait of Gibraltar could explain the hominin remains at Barranco León in southeastern Spain (1.4 Ma) and Sima del Elefante in northern Spain (1.2 Ma). But the site of Pirro Nord in southern Italy, allegedly from 1.3 – 1.7 Ma, suggests a possible arrival from the East. Resolution is insufficient to settle the matter.

Strait of Sicily

Passage across the

was suggested by Alimen (1975) based on the 1973 discovery of Oldowan grade tools in Sicily. Radiometric dates, however, have not been produced, and the artefacts might as well be from the Middle Pleistocene, and it is unlikely that there was a land bridge during the Pleistocene.

Causes for dispersal

Climate change and hominin flexibility

For a given species in a given environment, available resources will limit the number of individuals that can survive indefinitely. This is the

carrying capacity The carrying capacity of an ecosystem is the maximum population size of a biological species that can be sustained by that specific environment, given the food, habitat, water, and other resources available. The carrying capacity is defined as the ...

. Upon reaching this threshold, individuals may find it easier to gather resources in the poorer yet less exploited peripheral environment than in the preferred habitat. ''Homo habilis'' could have developed some baseline behavioural flexibility prior to its expansion into the peripheries (such as encroaching into the predatory guild). This flexibility could then have been positively selected and amplified, leading to ''Homo erectus'' adaptation to the peripheral open habitats. A new and environmentally flexible hominin population could have come back to the old niche and replaced the ancestral population. Moreover, some step-wise shrinking of the woodland and the associated reduction of hominin carrying capacity in the woods around 1.8 Ma, 1.2 Ma, and 0.6 Ma would have stressed the carrying capacity's pressure for adapting to the open grounds. With ''Homo erectus'' new environmental flexibility, favourable climate fluxes likely opened it the way to the Levantine corridor, perhaps sporadically, in the Early Pleistocene. There is

evidence Evidence for a proposition is what supports the proposition. It is usually understood as an indication that the proposition is truth, true. The exact definition and role of evidence vary across different fields. In epistemology, evidence is what J ...

that the Mid-Pleistocene Revolution facilitated mammalian turnovers during the Late Early and Early Middle Pleistocene that may have included the hominin dispersals observed in the

fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

around this time.

Chasing fauna

Lithic analysis In archaeology, lithic analysis is the analysis of stone tools and other chipped stone artifacts using basic scientific techniques. At its most basic level, lithic analyses involve an analysis of the artifact's morphology, the measurement of v ...

implies that Oldowan hominins were not predators. However, ''Homo erectus'' appears to have followed animal migrations to the north during wetter periods, likely as a source of scavenged food. The sabre-tooth cat '' Megantereon'' was an

apex predator An apex predator, also known as a top predator or superpredator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the hig ...

of the Early and Middle Pleistocene (before MIS 12). It became extinct in Africa c. 1.5 Ma, but had already moved out through the Sinai, and is among the faunal remains of the

Levant The Levant ( ) is the subregion that borders the Eastern Mediterranean, Eastern Mediterranean sea to the west, and forms the core of West Asia and the political term, Middle East, ''Middle East''. In its narrowest sense, which is in use toda ...

ine hominin site of Ubeidiya, c. 1.4 Ma. It could not break

bone marrow Bone marrow is a semi-solid biological tissue, tissue found within the Spongy bone, spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It i ...

and its kills were likely an important food source for hominins, especially in glacial periods. According to this hypothesis, hominins would also have successfully competed with the kleptoparasitic giant short-faced hyena, '' Pachycrocuta'', for these carcasses. In colder Eurasian times, the hominin diet would have to be principally meat-based and Acheulean hunters must have competed with cats. Some papers have argued against this hypothesis, showing that the dispersals of hominins from Africa into Eurasia were asynchronous with those of other land mammals and that the latter was thus unlikely to be the cause of the former.

Coevolved zoonotic diseases

Bar-Yosef and Belfer-Cohen suggest that the success of hominins within Eurasia once out of Africa is in part due to the absence of zoonotic diseases outside their original habitat. Zoonotic diseases are those that are transmitted from animals to humans. While a disease specific to hominins must keep its human host alive long enough to transmit itself, zoonotic diseases will not necessarily do so as they can complete their life cycle without humans. Still, these infections are well accustomed to human presence, having evolved alongside them. The higher an African ape's population density, the better a disease fares. 55% of chimps at the Gombe reserve die of disease, most of them zoonotic. The majority of these diseases are still restricted to hot and damp African environments. When hominins moved out into drier and colder habitats of higher latitudes, one major limiting factor in population growth was removed.

Physiological traits

While ''Homo habilis'' was certainly bipedal, its long arms are indicative of an arboreal adaptation. ''Homo erectus'' had longer legs and shorter arms, revealing a transition to obligate terrestriality, though it remains unclear how this change in relative leg length might have been an advantage. Sheer body size, on the other hand, seems to have allowed for better walking energy efficiency and

endurance Endurance (also related to sufferance, forbearance, resilience, constitution, fortitude, persistence, tenacity, steadfastness, perseverance, stamina, and hardiness) is the ability of an organism to exert itself and remain active for a ...

. A larger ''Homo erectus'' would also dehydrate more slowly and could thus cover greater distances before facing thermoregulatory limitations. The ability for prolonged walking at a normal pace would have been a decisive factor for effective colonisation of Eurasia.

Effects

The appearance of early hominins in Eurasia coincided with a reduction in the diversity of the continent's carnivore guild. It has been postulated that this was related to the Oldowan-Acheulean transition, as the development of Acheulean technology signifies a change in human ecology from a passive, scavenging role to that of more active predation.